Motor-controlling system.



E. L. GALE, SR. MOTOR CONTROLLING SYSTEM.

APPLICATION FILED NOV. 18, 1911.

Q 7 i [Me so woe Wfoz in. 15 6M Patented July 29, 1913.

UNITED STATES PATENT OFFICE.

ERNEST E. GALE, $3., or YONKERS, NEW YORK, AssrGuon To one ELEVATOR00mm, or JERSEY CITY, NEW JERSEY, A conronsrron or NEW JERSEY.

MOTOR-CONTROLLING SYSTEM,

Specification of Letters Patent.

Patented July 29, 1913.

Application filed November 18, 1911. Serial No. 660,980;

To all whom it may concern:

Yonkers, in the county of Vestchester and State of New York, haveinvented a new and useful Improvement in Motor-Control- .lingSystems,'of which the following is a specification.

My invention relates to controlling systems for electric motors and isparticularly adapted to the control of an alternating current hoistin orelevator. motor but it is applicable to the control of electric motorsin general.

One of the objects of my invention is the provision of simple andefficient means for automatically effecting the acceleration of analternating current mot-or according to the loadand speed.

Another object of the invention is the provision of means for retardingthe motor in stopping and for automatically varying the retardation soas to meet all conditions of load and speed.

A further object of the invention is the provision of a dynamo electricmachine coupled to the hoisting motor and arranged automatically tocontrol the latter both in,

starting and stopping.

Other objects will appear hereinafter, the novel combinations ofelements being pointed out in the appended claims.

In the accompanying drawing, Figure 1 represents diagrammatically myinvention applied to an electric elevator system; Fig. 2 represents amodification of the electric generator shown in Fig. 1.

-.lt is well known to those versed in electrical matters that the use ofanalternat-ing current system of distribution is being more widely usedevery day owing to certain advantageous characteristics it possessesover the older system of direct current distribution and for this reasonalternating currentmotors are used for power purposes to a very largeextent. One of the chief difliculties in connection with the operationof alternating current motors and particularly where such motors areused'for hoisting purposes or for driving elevators is that no efiicientand practical method has been devised for effecting a retardation of themotor in stopping. In the caseof direct current motors this difficultyis readily overcome since a direct current motor will act as a generatorwhen driven by the load and 'by' perm tting the same to send currentthrough a resistance element any desired degree of retardation may behad, the energy consumed being given out as-heat. This method which hasproven very effective in the case of direct current motors is notavailable where alternatingcurrent motors are used since the commercialalternating current motor will not act as a self exciting dynamo. Forthis reason it has been found necessary to employ a heavy and powerfulspring applied friction brake and to rely entirely on this for slowingdown and stopping the motor. While'this arrangement answers thepurpose'fairly 'well where the motor is of small size, it is far fromsatisfactory when used with amotor of appreciable size such as isrequired to drive an elevator since the rotor of'an elevator motor isnormally heavy and of high peripheral speed which places an excessiveduty on the mechanical brake in stopping and has thus limited the sizeand speed. of the motor which could be brought to rest within thelimiting conditions of satisfactory"elevat or service and has inconsequence limited the-s eed of elevator cars operated by alternatlngcurrent motors. Furthermore it has been proven in practice that thesevere duty which {the mechanical brake must perform makes it necessarycontinually to adjust the same owing to excessive wear on the brakeshoes or bands. The invention which I am aboutto describe overcomes thisinherent lack of dy? namic braking eifect in alternating current motorsby employing a direct current generator mechanically coupled to thealternating current motor and using the current generated thereby toeffect the desired dynamic braking action, and means actomatically toregulate or control the retardation due tothis dynamicqbrake to suitvarying conditions of load and speed and I further purpose to utilizethe current from the generatorfor effecting the automatic control of themotor in starting and accelerating to full normal speed.

Referring to the drawings, M designates an alternating current hoistingmotor which is connected through the usual worm gear transmissioncontained in the gear casing F to the elevator car C. The ordinarycounterbalance or back drum Weight is shown at W. The electricallyreleased mechanical brake apparatus is designated by B while Grepresents a direct current generator which is mechanically coupled tothe motor lid and driven thereby. The motor M is provided withsli-prings K which are connected to a starting resistance R controlledby an accelerating magnet A.- A hand switch S in the car is used tostart, stop and reverse the hoisting motor through the reversingswitches U and D. At the top of the reversing switches is shown a switchJ which is for-the purpose of reversing the armature connections of thegenerator Grevery time its direction of rotation is changed, the switchJ being operated by the reversing switches' A slow down magnet Hcontrols a resistance I in the field circuit of the generator and it isoperated by current from the generator during the period of stopping.

E represents a stop motion switch whose function is to effect thestoppingot the hoisting machinery when the car reaches its limit oftravel in either direction. A main line switch L connects the systemwith any suitable source of alternating current supply.

In order to operate the elevator car in an upward direction, the handleot the switch S is moved to the left until it electrically engages thecontact 17. A circuit is thereby closed to the magnet winding of thereversing switch U this circuit being traced from the main 1, throughthe car switch contact 17 magnet winding of switch U, contact 18 of thestop motion switch E, contact ring 19, and by contact 20 to the main 2.The reversing switch U being now energized will operate to raise itscore and close the contacts 5, 4 and 6, thereby establishing a circuitto 'the'motor M through the conductors 9, 1 and 10 and to the releasingmagnet of the brake B. It will be observed that when the reversingswitch U is energized and its core moves upwardly the projection 21carried by the core rocks the lever 11 of switch J about its pivot 11and thereby closes the contacts 12 and 13 respectively which in turnestablish an electrical connection between the brushes 23 and 24 of thegenerator G and the terminals of the generator shunt field 22. Thiscircuit may be traced from the brush 23 to and through the contacts 13by wire 25 and by the wire 27 to oneterminal of the field winding 22.The

other brush 24 is connected through the wire 28, contacts 12 and wire 29to the opposite field terminal, hence it is seen that the field of thegenerator is connected across the generator armature through the switchJ. The closing of the reversing switch contacts 6 connects the windingof the accelerating magnet A across the generator armature throughtheconductors 29 and 27. Under these conditions the motor M starts torotate and move the elevator car upwardly. its speed being limited bythe resistance R which is connected in the rotor circuit through thesliprings K. As the motor starts, the generato-r will'act as aself-exciting dynamo and will, supply current to the accelerating magnetA, the potential of this generated current increasing as the speed ofthe motor M increases until the inagnet A becomes sutliciently energizedto raise the switch 30 thereby short circuiting a portion of theresistance It. This results in an increase in motor speed followed by anincrease in potential on the generator circuit which enables the magnetA to operate the switch 3]. and shortcircuit a further portion of thestarting resistance R. The motor now further increases its speed and themagnet A operates the. switch 32 to short circuit the remainder of thestarting resistance whereupon the hoisting motor assumes'full speed withshort circuited rotor and the caris raised at normal-running speed. Asthe car approaches its upward limit of travel the stop motion ring 19,which is operated by the usual traveling nut carried-on the drum shaftstarts to rotate inan anti-clockwise direction until just as the carreaches its upward limit the ring rotates out of electrical engagementwith the contact 18, thereby interrupting the circuit from the mains 1and 2 to the magnet winding of the reversing switch. The latterimmediately becomes denergized and opens the motor and brake releasingcircuits at the contacts 5 and 4 and at the same time interrupts thecircuit from the generator to the accelerating magnet A at the contacts6 and this magnet becomes deenergized and permits the switches 30, 31and 32 to open and thereby remove the short circuit around theresistance R and placing it in proper condition for again starting themotor. 'Upon the deenergization of the reversing switch magnet the'contacts 7 were closed and the generator is thereby connected to thestopping magnet H and to a stopping field 33 and resistance 1 in seriestherewith. This stopping field circuit may be traced from the generatorbrush 23, wire 25, contacts 13 of switch J, wire 27, contacts 8 and 7 ofthe reversing switches, wire 34, resistance I. stopping field 33, wire29, contacts 12 of switch J, and by wire 28 to the generator brush 24:.The magnet H is at the same time connected across the generator armaturethrough the conductors'34 and 29. rent-dependent upon the speed of themotor M now flows through the stopping field and resistance I and thegenerator exerts a strong retarding efi'ect on the motor. The retardingaction of this external power consuming device will depend upon thespeed of the motor but will not be directly proportional to the speedsince'the voltage of the generator will be built up more rapidly thanthe increase in speedofthe generator owing to the increase in fieldstrength as well as to A curmitting a greater current to flow,

the increase in speed of the armature. This will result in an increaseof the retarding action in-a greater ratio than the increase in speed ofthe motor. But the retarding action required to bring the moving partsto rest within a given distance also increases at a greater ratio thanthe increase of speed in said parts. This increased retarding action ofthe generator is therefore advantageous in bringing the parts uniformlyto rest within a given distance even when the speed of the motor isaffected by the load. The generator may be designed to produce thisvariation in any desired degree, such variation being reduced to aminimum by having a shunt winding producing a saturated magnetic field.

The magnet H which controls the resistance. I is connected across thegenerator brushes and is therefore controlled directly by the generator.This magnet will operate to close the switches 35 and' 36 in the ordernamed to short circuit more or less of the resistance I and therebyreduce the resistance in the stopping field circuit and perthusincreasing the dynamic brake action. The action ,ofthe magnet H isentirely automatic and the amount of resistance cut out thereby-dependson the speed of the motor M, the I magnet H effecting a graduatedbraking effect which is particularly desirable in the case of fastrunning elevators.

By the use of the generator arranged and connected as shown it hasbeenfound that the mechanical brake may be of comparatively moderate poweror just a little more than sufficient to hold the motor against movementwhen stopped and prevent it from being rotated backward by the loadsince the generator will brin the motor running at full speedsubstantially to rest. One great advantage of this is to permit the useof a relatively small mechanical brake since its duty is very light andconsequently its life is long and it is subjected to little wear.

I have pointed out the stopping. of the apparatus by means of the stopmotion switch The action is the same as already pointed out except thatthe reversing switch magnet will be decnergized at the contacts of theswitch S instead of the contacts of the stop motion switch.

The operation of the reversing switch, D is efi'ected by moving the carswitch lever in a right hand direction, thereby closing a circuit to themagnet winding of said switch and the latter will establish the motorcircuit precisely as the switch U did excepting that the leads 9 and 10will be interchanged cuits.

or reversed so as to cause the motor to reverse its direction ofrotation and cause the elevator car to descend.

As before pointed out, the switch J is for the purpose of maintaing thepolarity of the generator field the same regardless of the direction ofrotation of the motor and this switch'isthrown from one side'to theother by the operation of the reversing switches. The weight 14 iscarried past the center 11 whenever the switch is thrown over and itsfunction is to maintain the contacts 12,13 or 15, 16, respectively, inclosed relation.-

Another method of maintaining the polarity of the generator the same isillustrated in the modification shown'in Fig. 2. Here the generatorbrushes 23 and 24 are carried by a ring 37 which is arranged to rotatein a frame 451 secured to the motor. The ring '37 carries a stop piece38 which engages fixed stops 39, 39 spaced substantially 180 apart.Should the motor rotate in a clockwise direction, the friction of thebrushes 23 and 24 on the commutator 40 will cause the ring 37 to rotatewith it until the stop piece 38 engages the lower stop 39, the brush 23now occupying the position formerly occupied-by the brush 24. .It isself evident that the interchange of brushes due toa reversal ofrotation will maintain the polarity of they field the same under allthermore I have for the sake of illustration shown a three-phase systemof alternating current, but my invention isnot confined to anyparticular phase and may be used if so desired with a direct currentsystem of cirlVhat I claim as new and desire to have protected byLetteis Patent of the United States is 1 1. The combination with amotor, of a generator mechanically coupled thereto, a resistancein thecircuit of said generator, means for closing'said circuit, andmeansoperative upon the closure of said circuit to reduce said resistance anamount controlled by the speed of the motor.

2. The combination with a motor, of a generator operatively connectedthereto, re-

sistance in'the circuit of said generator, means for closing saidc1rcu1t, and means controlled by said generatorand responsive resistancein the circuit of said generator,

means for closing said circuit, and means controlled by saidgeneratorfor automatically effecting a gradual reduction of said resistance. I

' 4. The combination with a motor, ,of a generator driven thereby, anadditional field for said generator, and means controlled by thegenerator for regulating the strength of said additional field, andthereby regulating the retarding action ofthe generator on the motor.

5. The combination with an alternating current motor, of a generatordriven thereby, a plurality of fieldwindings for said generator, aswitch for closing a circuit to said motor-when in oneposition and forclosing a circuit from the generator through one of the generator fieldswhen in another position, and means for automatically varying thegenerator current through said field.

6. The combination with an alternating current motor,- of a compoundwound generator driven thereby, a resistance-in one of the fieldwindings of said generator, andmeans controlled by the generator forgradually varying said resistance, and thereby controlling the action ofthe generator on the motor.

7. The combination with an alternating current motor, of a dynamic braketherefor comprising a generator coupled to the motor,

a field winding arranged to excite said gen-- orator whenever the sameis rotated, an additional field winding for said generator, and

means controlled by said generator for varying the strength of saidadditional field to effect a graduated brake action on the motor.

8. The combination with an alternating current motor, of a generatordriven thereby, resistances in the motor and generator circuits, andmeansautomatically controlled by the generator for varying both of saidresistances to efi'ect a graduated start and stop of said motor.

9. The combination with an alternating current motor, of'a dynamic braketherefor comprising a generator driven thereby, resistances in the motorand generator circuits, and independent means controlled by saidgenerattr for efiecting the gradual short circuiting of said resistancesto start and stop the motor.

10. The combination with an alternating current motor, of a dynamicbrake therefor comprising a generator driven by the motor,

resistances in the motor and generator circuits, and separate meanscontrolled by current from said generator for automaticallyshort-circuiting said resistances gradually to start and stop said motorsubstantially as described.

11. The combination with an alternating current motor, of a generatordriven there by, reversing switches for closing the cir- 'cuit to afield winding of said generator, an additional field winding for saidgenerator, contacts on said reversing switches forclosing a circuit tosaid additional field Winding when the reversing switches are in aposition to open circuit the motor, and means con trolled by thegenerator for varyin the strength of said additional field to edect agraduated retarding action on the motor.

.12. The combination with an alternating current motor, ofa dynamicbrake therefor comprising a generator driven by said mot-or, automaticmeans operated by the generator for effecting the acceleration of themotor, and independent means controlled by the generator forautomatically regulao, ing'the dynamic brake action of the generator'onthe motor in stopping.

13. The combination with an alternating current motor and asupply-circuit therefor, of a dynamic brake for the motor comprising agenerator driven by the motor, means for controlling the starting andstopping of said motor. a switch operated by said controlling'means andadapted to maintain the polarity of the generator field the sameregardless of the direction of rotation of the motor, an additionalfield winding for said generator which is open circuited during theoperation of the motor, means controlled by said motor controllin meansfor closing the circuit of said additional field' winding to effect aslowing down of the motor when the latter is disconnected from thesupply circuit, and automatic means controlled by the generator forvarying the resistance of the circuit of said additional field winding.

14. The combination with an alternating current motor, of a dynamicbrake therefor comprising a direct current generator 0 adapted to rotatewith the motor, reversing switches for said motor, a switch for saidgenerator controlled by said reversing switches and adapted to controlthe direction of current flow through a field winding of the generator,and automatic speed controlled means to vary the resistance of thegenerator field circuit and thereby vary the dynamic braking action.

15. In an elevator, the combination of a 5 hoisting motor therefor,electro-responsive devices for controlling said motor, a generatorconnected to'rotate with the motor, an additional field winding for thegenerator, andv means controlled by the enerator for regulating thestrength of said additional field and thereby regulating the retardingaction of the generator on the motor.

16. In an elevator, the combination of an alternating current hoistingmotor, a generator driven thereby, resistances in the motor andgenerator circuits, and means automatically controlled by the generatorfor varying both of said resistances to effect a gradual start and stopof said hoisting motor.

17. In an elevator, the combination of an.

alternating current hoisting'motor, of a dynamic brake thereforcomprising a generator driven by the motor, resistances in the motor andgenerator circuits, and separate means controlled by current from saidgenerator for automatically short-circuiting said resistances graduallyto start and stop the hoisting motor, substantially as described.

18.In an elevator, the combination of an alternating current hoistingmotor, of a dynamic brake therefor comprising a'generator driven by saidmotor, automatic means operated by acceleration of the motor, andindependent means controlled by the generator for automaticallyregulating the dynamic brake action of the generator on the hoistingmotor in stopping.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

. ERNEST L. GALE, SR.

Witnesses:

EDWARD H. STEELE, GEORGE D. Rosa.

the generator for effecting the 15'

